Process of treating cellulose acetates to alter the solubilities thereof and products of said process.



No Drawing: Original application filed October 2, 1911, Serial No.'652,442. Divid filed August 1, 1913.

UNITED STATES PATENT orrio HENRY DREYFU-S, 0F BASEL, SWITZERLAND.

PROCESS OF TREATING CELLULOSE ACETATES TO ALTER THE SOLUBILITIES THEREOFAND PRODUCTS 0F SAID PROCESS.

To all whom it may concern:

'Be it known that I, HENRY DREYFUS, a citizen of the Republic ofSwitzerland, re-

siding at Basel, Switzerland, have invented certain new and usefulImprovements in Processes of Treating Cellulose Acetates to Alter theSolubilities Thereof and Products of Said Processes, of which thefollowing is a specification.

The object of the present invention is to provide a treatment of certaincellulose acetates, insoluble in chloroform, but soluble inalcohol-chloroform and in alcoholtetrachlorethane, and soluble inconcentrated or somewhat diluted acetone, said acetates having beenobtained by a direct aeetylation process without passing through achloroform-soluble stage, whereby to produce cellulose acetates havingcertain other desired solubilities, which products are capable of use inthe manufacture of films, threads, varnishes and plastic bodies of allkinds.

I have discovered that. by treating the aforesaid cellulose acetateswhich are. insoluble. in chloroform, but which become very soluble, onthe addition of more or less alcohol to the chloroform, and" which aresoluble in concentrated acetone, or are soluble in acetone containing asmall percentage of water, with either organic or inorganic acids, oracid salts, or mixtures of these, and preferably by allowing thereaction to continue for a considerable time in the original acetylizingsolution 'or any equivalent solution, with or without the addition ofwater, acids,'or other agents which have the same effect in destroyingthe acetylizing'action of the acetic anhydrid without preventing afurther reaction for the formation of the successive solubilities invarious solvents, and by then interrupting the action at the time whenthese different desired sol'ubilities have been produced, and before thesame disappear, a series of valuable products can be obtained. Y

These products, obtained by interrupting the action at successive stagesthereof, are distinguished from each other, and from the celluloseacetate-s forming the starting material of the process, and from allcellulose acetates heretofore known, by their solubilities in any one ofseveral solvents singly, or in mixtures thereof.

Specification of Letters Patent.

d and this application Serial No. 782,530.

treatment of) the products produced in ac cordance with the processdescribed in my copending application, Serial No. 652,442 (now U. -S.Patent #1,l8l,857), of which the present case is a division or by thedirect acetylation processes described I in my French Patents 432,046and 478,023. The products of said parent application are particularlydistinguished in that while'they are insoluble in chloroform, or intetrachlorethane alone, they are readily soluble by the addition ofalcohol to these chlorinated hydrocarbons, and are readily soluble in aconcentrated acetone, or else in acetone containing a relatively smallpercentage of water. The 'productsproduced in accordance with my presentinvention are distinguished from the cellulose acetates heretoforetechnically known, in that they give solutions in acetone, which aremore viscous than any heretofore produced, so that-such solutions can beused for making films and for making celluloid substitutes, assubstitutes for nitro-cellulose, having all the properties required formaking good films and good celluloid substitutes. The solutions inacetone are highly viscous, clear, very concentrated, while the hithertoproduced prod uct's' give solutions in acetone, of which the viscosityvaries from that of water only up to that of a syrup. The celluloseacetates heretofore produced inmost cases do not cellulose acetateswith' dilute acid, such as sulfuric acid, are more or lesssoluble indilute alcohol whencold, which solutions spread out on glass plates givetransparent films, which when dried are not brittlebut are elastic andcan be folded a considerable number of times at the same ,point withoutbreaking, while by a similar treatment of cellulose acetates soluble inchloroform and" made by direct acetylization, dissolving? in alcohol,spreading out and drying products are produced'which are'opaque to"whitish masses or fragments of films, which are very brittle.

Another important feature of the present invention is that the originalcellulose emderivatives of cellulose can acetylizing action, butincapable of preventing the desired changes in the solubility). Also thecellulose acetates being treated may be dissolved in an equivalentsolutlon,

to produce a solution of the specified cellu-- lose acetates contalningorganic or IIIOIgELIIIC acids, or acid salts or mixtures thereof, andalso if necessary with the addition of agents which are capable ofpreventing further 'acetylization of the cellulose acetates, withoutpreventing the further reaction for the formation of the successivesolubilities herein described. This action is allowed to proceed, untilthe treatment of test porthat the desired solubilities exist. By thistreatment, and by interrupting the same at the time when the desiredsolubilities exist, a series of new acetylated be obtained, whichderivatives can be distinguished from each other and fromthe startingmaterial tions shows and from other cellulose acetates, theirsolubilities in oneor in several solvents or in mixtures of certainsolvents. Also the solubility of these products in each of the differentsolvents and mixtures of solvents,

is progressively modified as the duration of the reaction is prolonged.

During the reaction, the products become (in addition to the existingsolubility in acetone) progressively more easily soluble inchloroformalcohol, and simultaneously solubilities in diluted alcoholand in alcohol-benz'ene are developed. On continuing the reaction, thesolubility in alcohol-benzene again decreases and disappears, while thesolubilities in diluted alcohol and in acetone still continue. This maybedemonstrated, by testing samples at successive stages of this secondreaction. Later on, the solubility in pure acetone, or in any acetonesolution containing over 80% of pure acetone, disappears, while asolubility in diluted acetone is successively more and more developed,so that the longer the duration of the process, the larger the amount ofwater that must be added to the acetone, in order to dissolve theproduct; until finally a product soluble in hot water, or in aqueoussolutions is obtained. Besides these solubilities successively decreasesand finally from the beginning the solubility inalcohol-tetrachlorethane, and in certain other solvents progressivelyincreases, throughout the time of the second reaction. Also the relativeproportions of the constituent parts of mixtures of solvents such asalcohol and chloroform, in the mixture which will most readily dissolvethe product will progressively change. During the stage in which theproduct is soluble in alcohol-benzene, the products are very soluble inhot diluted alcohol (up to to 80% or even more) and are of greatimportance;

These products if submitted to the said treatment while in aprecipitated form will produce. very concentrated solutions of celluloseesters in dilute alcohol, which on cooling will give completelytransparent masses. Such a solution in hot alcohol, spread out on aglass surface congeals almost immediately and after drying gives a filmof most excellent quality which is very pliable, and may be folded manytimes at the same point without breaking.

These same products give transparent, viscous, solutions in hotalcohol-benzene, which on cooling, set and form coherent and completelytransparent masses, and if these hot solutions are run onto a glassplate, films are produced which are of a remarkable quality (beingtransparent, instead of whitish and powdery masses).

The principle of the present process is also to interrupt the reactionin any one of the different phases of solubilities, in order to changeprogressively with the duration of the reaction, the solubilities in thedifferent solvents or in mixtures thereof.

Also the use of a cellulose acetate of the kind herein described, whichis insoluble in chloroform, gives the great final advantage,

that the resulting products give much'more chloroform.

I have moreover found that in carrying out this second reaction in theoriginal acetylizing solution, or in similar solutions, the formation ofthese products soluble in the various solvents or mixtures thereof canbe accelerated or made slower by changing one or more of the conditionssuch as by raising the temperature of the original acetylizing solution,or by increasing the amount of Water, mineral acids or other acids, oracid salts, or mixtures-thereof.

By prolonging the action of the original acetylizing solution, (as leftwhen a product insoluble in chloroform has been produced, with orwithout the addition of water or other suitable substances thereto) Ican convert either the aforesaid cellulose acetates insoluble inchloroform into cellulose acetates soluble therein (said products notbeing the chloroform-soluble products made by a direct acetylat'ionprocess, but by the secondary process herein described, and whichproducts are different in their behavior with other solvents than thosechloroform-soluble products heretofore known and made by a directacetylation process) or the reaction in the present process can becarried out also in a different" manner in such a way thatthe productsremain always insoluble invchloroform while the solubilities in othersolvents will progressively change.

If water is'addedto the original acetylization of the cellulose acetate(that is to say, the solution in the original acetylation mixture) theamount of added water should preferably not be morethan 30 to 35%, andin many cases much less water, say up to 5 to 10% or up to 20% issuflici'ent. Water may be omitted entirely if so desired or replaced byalcohol, or by other substances having a similar effect. Theproductsproduced according to my process, which while being soluble in acetoneand particularly those products which are simultaneously soluble inacetone, alcohol-benzene, chloroform, and chloroform-alcohol, etc.,cannot be produced when using a quantity of water over about 30 to 35%,or eventually products which are simultaneously soluble in all theaforesaid solvents with the exception of chloroform, (in which they areinsoluble) cannot be produced when using a quantity of water materiallygreater than 35%, but are produced by certain modifications of myprocess, as described below.

Even when using 30 to about 35 parts of water this amount is too much inmy process for producing the especially important solubilities abovereferred to, which are roduced only when using smaller quantities ofwater. I

In my process, I operate upon a cellulose acetate which is insoluble inchloroform, and I have found that good results vcan be obtained withquantities of water of less than about 30 to 35%, (especially when usingabout 20 to 30% or 5 to 20%) (based upon the amount of celluloseemployed giving good results), especially when using a cellulose acetateproduced when employing about 250 parts of acetic anhydrid and 10 to 15parts of sulfuric acid, per 100 parts of cellulose.

If instead of using sulfuric acid, the further reaction is effected byusing. weakeracids (such as organic acids) or other similarly actingagents, or if the quantity of sulfuric acid is diminished more and more,these proportions may be varied between certain restricted limits, thesmaller the amount of sulfuric acid the larger the amount of water orits equivalent. Consequently if only organic acid is present, a largeramount of water can be used. All these products show different behavior,according to whether they have been produced with larger or smalleramounts of water or other similarly acting materials, (which effect isindependent of the difference in solubilities produced by prolonging"the said secondary reaction). It may also be stated that in my process1t is not necessary. to add any water.

varying'solubilities or acids but products of may be produced byallowing the acetylizing reaction to proceed without adding anything .tothe solution, and interrupting the reaction when the different desiredsoluy biliti'es exist. -In-this latter case the resulting products areespecially of interest when the original acetylizing reaction "hasbeeniefl'ected with relatively small quantities of acetic anhydrid, sothat no free anhydrid;

is presentafter the completion of the acetylizing reaction. In thismodeof procedure the reaction can be interrupted, by the addition, ofalcohol, and substances havingya similar-eflect.

If the amount of aceticanhydrid is in-" creased, the amount of water tobe added maybe increased in corresponding molecular pro-portiondepending upon the amount of moisture in the original cellulosefor othermaterial employed. I I I Y In place of water, other agents may be usedwhich are capableof neutralizing (so far as acetylization is concerned)the acetic anhydrid, but which will not act to prevent the formation ofthe desired changes insolubility. Such bodies as hydroxyl derivatives,

'oxyacids, alcohols, etc., may be used, but

such substances possess no advantages over water, and aremore-expensive, and are accordingly not to be generallv recommended.

In this manner products may be produced which are soluble in acetone,soluble in alcohol-benzene, in alcohol-chloroform, and in chloroformsimultaneously, and which by. ,further prolonging the reaction losetheir solubility in chloroform while retaining for a time the othersolubilities mentioned, or products can be directly produced withoutpassing through a stage of being soluble in chloroform, which aresoluble in acetone, soluble in alcohol-benzene, and inalcohol-chloroform, but insoluble in chloroform. Such products are ofgreat value.

. If on the other hand morewater is used,

while still observing the proportions of 2%} toll then the reaction canbe carried out ina different manner, depending upon the increase of theamount of lent,.over thatabove stated, whereby products can be directlyproduced which have other solubilities but which are insoluble inacetone.

Products soluble only in dilute acetone but insoluble inalcohol-benzene, soluble in alcohol-chloroform, and insoluble inchloroform may thus be prepared, "or products soluble in dilute acetone,insoluble in chlo- 130 water or its equivarofo-rm', insoluble inalcohol-benzene, and even insoluble in alcohol-chloroform may beproduced.

The reaction can be accelerated by raising the temperature, or byincreasing the. quantity of mirferal acids if used. Thus if sulfuricacid is used as the mineral acid, (instead of for example organic acidsalone) in the original acetylization, in amount equal to 10 to 25%, amore rapid reaction will take place than would be the case if only about3% of sulfuric acid were used, (the other conditions being the same).

The length of time necessary for the re action to produce the desiredsolubilities, will vary according to the conditions, and may amount to afew hours only, or it may be 10 to 20 hours, or from 2 to 4 days, oreven much more, depending upon the different conditions. In this way, itis possible to isolate products having the finest difference ofsolubilities.

The preparation of those cellulose acetates to be employed in thepresent process and which are insolublein chloroform, (as startingmaterials for the present process) is preferably effected inaccordance'with the directions given in my copending application652,442, or according to my French Patents Nos. 432,046, and 478,023 andthese products can be prepared either in solution or in suspension.Generally, all cellulose acetates, which are insoluble in chloroform,but which are soluble in alcohol-chloroform, and which have beenproduced by a direct acetylation process without passing throu a stageof being soluble in chloroform, during this acetylation process, can beused, either in the original acetylizing solution, or in precipitatedform, or suspension.

In order to illustrate my invention I give the following example, theparts being by weight, but it is to be noted that the invention is notlimited to this example, which is given for the purpose of illustrationonly, for making the invention clear.

E wample.

A solution of cellulose acetate, as directly produced, for example by'treating 100 parts of cellulose, 400 parts of glacial acetic acid, andabout 250 parts of acetic anhydrid, and 10 to 15 parts of sulfuric acid,by directly introducing the cellulosic material containing about 5 to 6%of moisture, as in my parent application, into this acetylizing mixture,at a relatively low temperature or by progressively introducing theacetic anhydrid into the mixture of the acetic acid, sulfuric acid andcellulose, according to French Patents No. 432,046 or 478,023, or anyother solution of a cellulose acetate which is insoluble in chloroformand which has been produced by a direct acetylation process containingorganic or .inorganic perature,

acids or acid salts or mixtures thereof, is allowed to stand at aboutordinary temuntil a test portion indicated the existence of the desiredsolubilities, whereupon the acetate is precipitated, washed and dried.

If in this example the amount of water used is equal to'about 5 to 10%,or even up to 20% of the weight of the cellulose employed, and if the.mixture is allowed to stand at a temperature of about 20 0., thefollowing changes in solubility may be observed. -The original materialbeing insoluble in chloroform, but soluble in concentrated acetone, orelse soluble in a somewhat diluated acetone, becomes soluble inchloroform, andthe reaction can then be interrupted.

After about 20 hours, besides the existing solubility in acetone, andchloroform a solubility in alcohol-benzene, and in diluted alcohol, andin ethyl acetate is developed to a high degree. After about 40 hoursthese solubilities are very great. The reaction can also be directed insuch a manner that the solubility in chloroform never appears, asdescribed below.

The reaction in the original acetylizing solution can also be carriedout in the following manner, by the addition of sufficient water todestroy the acetylizing effect vof the acetic anhydrid, and allowing themixture to stand until test portions indicate the desired solubilities.In this process one may employ an amount of water equal to 5 or 10%, orup to 20%, of the weight of cellulose employed. If more than about 30%to 35% of water is used, while the amount of sulfuric acid remains thesame, then a product soluble in chloroform, will not be produced, butthe product is insoluble in chloroform, although it will be soluble incertain other solvents, as above noted, for example inchloroform-alcohol, alcohol-benzene, concentrated acetone, dilutealcohol, etc. If 40%, or more of water is employed, (based upon theWeight of the cellulose employed) one can obtain directly a producthaving a solubility in diluted acetone, which does not have thesolubility in alcohol-benzene or some of the other solubilities abovestated, irrespective of how long the reaction is continued.

0 By diminishing the quantity'of sulfuric acid present by the additionof neutralizing agents, after the acetylization is completed,

or by using less sulfuric acid in the acetylizing reaction, the reactionisretarded, which effect is also produced by uslng only organic acids,but then this retarding can be balanced by a raising of the temperature,moreover the quantity of water can in these latter cases also beincreased.

These products are used for the manufacture of artificial silk,artificial horse-hair,

celuloid, films, artificial leather, insulating devices, varnishes,coatings and various other purposes.

The treatment of precipitated cellulose acetates to change theirsolubilities is not specifically claimed herein, but in my copendingapplication 73,496, filed Jan. 21, 1916.

What I claim is 1. A process of treating a cellulose acetate which isinsoluble in chloroform and in diluted alcohol, but soluble in acetone,which comprises subjecting such a cellulose acetate, while the same isin solution in the presence of an acid material, to the continued actionof such acid material until a product is obtained which is soluble indiluted alcohol of a predetermined concentration, and then stopping thereaction before said solubility disappears.

2. The process of treating a cellulose acetate insoluble in chloroformand'in alcohol of a predetermined concentration and in alcohol-benzene,which comprises treating the same with a solution containing acidformingions, ble in a liquid comprising alcohol of said predeterminedconcentration and soluble in alcohol-benzene, is produced, and thenstopping the reaction, before said solubilities disappear.

3. The process of treating a cellulose acetate insoluble in chloroformand "insoluble in alcohol-benzene, but soluble in acetone Whichcomprises treating the same with a dilute acid until uble inalcohol-benzene is produced and then stopping said reaction before saidsolubilities disappear.

4. The process of treating a cellulose acetate insoluble in chloroformand in alcoholbenzene, but soluble in acetone, which comprises treatingthe same with dilute mineral acid until a cellulose acetate soluble inace tone, and in alcohol-benzene, is produced as determined by tests atSuccessive stages of the process, and stopping the reaction before saidsolubilities disappear.

5. The process of treating cellulose acetates insoluble inchloroform andin diluted alcohol, but soluble in acetone and in alcohol-chloroform,which comprises treating the same with an acid until the celluloseacetates become soluble in diluted acetone, and in diluted alcohol.

6. A cellulose acetate soluble in acetone, giving therein highly viscoussolutions and soluble in alcohol-benzene, and soluble in dilutedalcohol, and. soluble in alcohol-chloroform.

7. A cellulose acetate soluble in acetone, giving therein highly viscoussolutions, and soluble in alcohol-benzene, and soluble in dilutedalcohol, and soluble in alcoholchloroform, and soluble in chloroform.

until a cellulose acetate solu-" a cellulose acetate soldratingcellulose,

tates insoluble in chloroform but soluble in solubililties, whichcomprises treating said cellulose ,acetates with a solution containingan acid, said solution containing less than 35 cellulose representedbythe cellulose acetate employed.

9. A process of treating a cellulose acetate which is insoluble inchloroform but soluble in acetone, which comprises subjecting the same,While in solution, to the action of an acid material having noacetylating action.

10. A process of treating a cellulose acetate, which is insoluble inchloroform, but soluble in acetone and in alcohol-chloroform bysubjecting the same while in solution to the action of an acid materialhaving no acetylating action, in the presence of water.

11. A process of treating a cellulose acetate which is insoluble inchloroform and insoluble in alcohol-benzene but soluble in acetone, bysubjecting the same, while in solution, to the action of an acidmaterial having no acetylating action. 4

12. A process of treating a cellulose acetate, which is insoluble inchloroform but soluble in a mixture of acetone and water, by subjectingthe same While in solution, in the presence of Water, to the action ofan acid material which has no acetylating action, whereby the amount ofwater present has an effect upon the solubilities developed by saidtreatment. I

13. A process of treating a cellulose acetate, which is insoluble inchloroform, but soluble in acetone by subjecting the same, While insolution in a solvent having no acetylating actionto the action of anacid material in the presence of water, whereby the quantity of waterdetermines the solubili-,

ties developed.

14. A process of treating a cellulose acetate which is insoluble inchloroform but soluble in acetone, which comprises subjecting the samewhile in solution in the presence of an acid solvent having noacetylating action, and in the presence of water, until a productsoluble in chloroform and soluble in acetone has been obtained and thenstopping the reaction while these solubilities exist.

15. A process of treating a cellulose acetate which is insoluble inchloroform, but soluble in diluted acetone, which .COIIIPIISQSsubjecting the same, while in solutlon, to the action of an acidmaterial having no acetylating action, until a product having dlfi'erentsolubilities from the starting material has been produced.

16. A process of producing cellulose acetates having particularsolubilities, being insoluble in chloroform, which compriseshythereafter acetylizing the parts of water to each 100' parts ofacetoneinto products having certain desired same at a relatively lowtemperature, and

thereafter subjecting the same, while in solution, to the action of anacid material free from acetylizing action, but capable of changing thesolubility of the cellulose acev tate.-

acting upon said hydrated cellulose, with an acetylizing agent at arelatively low tem- 'perature, to produce a cellulose acetate readilysoluble in alcohol-chloroform, but insoluble in chloroform alone andthereafter (3) adding to the solution of the cellulose acetate in theacetylizing solution, an agent capable of destroying the acetylizingaction of said acetylizing solution, and (4) allowing a secondaryreaction to proceed, until the solubilities of the cellulose acetatehave been changed.

18. A process of treating a cellulose acetate insoluble in chloroform,but soluble in chloroform-alcohol, which comprises treating the same insolution, with an acid, until a cellulose acetate simultaneously solublein alcohol-chloroform, acetone, chloroform, alcohol-benzene'and dilutealcohol is produced.

' Basle, the 19th of July, 1913.

In testimony whereof, I have hereunto subscribed my name.

DR. HENRY DREYFUS.

Witnesses:

PHILIP HOLLAND, ARNOLD ZUBER, EMIL DREYFUS.

